Salt-free composite marking based on chiral liquid crystal precursors comprising chiral acrylate dopants

Abstract

Disclosed is a substrate which has thereon a marking or layer comprising a salt-free cured chiral liquid crystal precursor composition which comprises one or more nematic compounds A and one or more chiral dopant compounds B which are capable of giving rise to a cholesteric state of the chiral liquid crystal precursor composition and are of formula (I) as set forth herein. A modifying resin made from one or more polymerizable monomers comprising an average of at least one ether functionality per polymerizable group is disposed between the substrate and the marking or layer and in contact with the marking or layer in one or more areas thereof. The modifying resin changes the position of a selective reflection band exhibited by the cured chiral liquid crystal precursor composition on the substrate in the one or more areas.

The invention claimed is: 
     
       1. A substrate having thereon a marking or layer comprising a chiral liquid crystal precursor composition that is cured, wherein the chiral liquid crystal precursor composition is salt-free and comprises (i) one or more nematic compounds A and (ii) one or more chiral dopant compounds B which are capable of giving rise to a cholesteric state of the chiral liquid crystal precursor composition and are of formula (I): 
       
         
           
           
               
               
           
         
         wherein: 
         R 1 , R 2 , R 3 , and R 4  each independently denote C 1 -C 6  alkyl and C 1 -C 6  alkoxy; 
         A 1  and A 2  each independently denote a group of formula —[(CH 2 ) y —O] z —C(O)—CH═CH 2 ; 
         m, n, o, and p each independently denote 0, 1, or 2; 
         y denotes 0, 1, 2, 3, 4, 5, or 6; and 
         z equals 0 if y equals 0 and z equals 1 if y equals 1 to 6; 
         wherein a modifying resin with ether functionalities comprising at least one unit of formula (II):
   —[CH(R 5 )—(CH(R 6 ))q-O]r-  (II)
 
 
         wherein q is 0 or an integer of from 1 to 4, 
         r is an integer of from 2 to 20, and 
         R 5  and R 6  are each independently hydrogen or C 1-4  alkyl 
         is disposed between the substrate and the marking or layer and in contact with the marking or layer in one or more areas thereof, the modifying resin increasing a position of a selective reflection band exhibited by the chiral liquid crystal precursor composition that is cured on the substrate in the one or more areas; and 
         wherein the marking or layer covers at least one area of the substrate not carrying the modifying resin. 
       
     
     
       2. The substrate of  claim 1 , wherein the one or more nematic compounds A comprise at least one compound that comprises at least one polymerizable group. 
     
     
       3. The substrate of  claim 2 , wherein the at least one polymerizable group comprises a group of formula H 2 C═CH—C(O)—. 
     
     
       4. The substrate of  claim 1 , wherein y in formula (I) equals 0. 
     
     
       5. The substrate of  claim 1 , wherein in formula (I) the total number of carbon atoms in R 1 , R 2 , R 3 , and R 4  does not exceed 8. 
     
     
       6. The substrate of  claim 1 , wherein in formula (I) at least two of m, n, o, and p denote 0. 
     
     
       7. The substrate of  claim 1 , wherein in formula (I) R 1 , R 2 , R 3 , and R 4  each independently denote C 1 -C 3  alkyl and C 1 -C 3  alkoxy. 
     
     
       8. The substrate of  claim 1 , wherein the ether functionalities are provided by alkyleneoxy units having from 2 to 4 carbon atoms. 
     
     
       9. The substrate of  claim 1 , wherein at least a part of the ether functionalities is provided by ethyleneoxy groups. 
     
     
       10. The substrate of  claim 1 , wherein the modifying resin comprises a dried aqueous resin. 
     
     
       11. The substrate of  claim 1 , wherein the modifying resin increases shifts a position of the selective reflection band exhibited by the chiral liquid crystal precursor composition that is cured, by at least 5 nm. 
     
     
       12. The substrate of  claim 1 , wherein at least a part of the selective reflection band exhibited by the chiral liquid crystal precursor composition that is cured and has been increased shifted by the modifying resin is in the visible range. 
     
     
       13. A method of providing a marking on a substrate, wherein the method comprises:
 a) applying onto a surface of the substrate a chiral liquid crystal precursor composition that is salt-free, wherein the substrate carries a modifying resin with ether functionalities comprising at least one unit of formula (II):
   —[CH(R 5 )—(CH(R 6 )q-O]r-  (II)
 
 
 wherein q is 0 or an integer of from 1 to 4, 
 r is an integer of from 2 to 20, and 
 R 5  and R 6  are each independently hydrogen or C 1-4  alkyl in one or more areas of the surface of the substrate, wherein the chiral liquid crystal precursor composition comprises (i) one or more nematic compounds A and (ii) one or more chiral dopant compounds B which are capable of giving rise to a cholesteric state of the chiral liquid crystal precursor composition and are of formula (I): 
 
       
         
           
           
               
               
           
         
         wherein: 
         R 1 , R 2 , R 3 , and R 4  each independently denote C 1 -C 6  alkyl and C 1 -C 6  alkoxy; 
         A 1  and A 2  each independently denote a group of formula —[(CH 2 ) y —O— z —C(O)—CH+CH 2 ; 
         m, n, o, and p each independently denote 0, 1, or 2; 
         y denotes 0, 1, 2, 3, 4, 5, or 6; and 
         z equals 0 if y equals 0 and z equals 1 if y equals 1 to 6; 
         in such a way that the composition covers at least a part of the one or more areas carrying the modifying resin and also covers at least one area of the surface that does not carry the modifying resin, 
         b) heating the chiral liquid crystal precursor composition to bring the chiral liquid crystal precursor composition to a chiral liquid crystal state; and 
         c) curing the chiral liquid crystal precursor composition in the chiral liquid crystal state; and wherein the modifying resin increases a position of the selective reflection band exhibited by the chiral liquid precursor composition that has been cured on the substrate in the one or more areas in which the modifying resin is present. 
       
     
     
       14. A substrate obtainable by the method of  claim 13 . 
     
     
       15. A method of changing increasing a position of a selective reflection band exhibited by a chiral liquid crystal precursor composition that is cured, wherein the chiral liquid crystal precursor composition is salt-free and comprises (i) one or more nematic compounds A and (ii) one or more chiral dopant compounds B which are capable of giving rise to a cholesteric state of the chiral liquid crystal precursor composition and are of formula (I): 
       
         
           
           
               
               
           
         
         wherein: 
         R 1 , R 2 , R 3 , and R 4  each independently denote C 1 -C 6  alkyl and C 1 -C 6  alkoxy; 
         A 1  and A 2  each independently denote a group of formula —[(CH 2 ) y —O] z —C(O)—CH═CH 2 ; 
         m, n, o, and p each independently denote 0, 1, or 2; 
         y denotes 0, 1, 2, 3, 4, 5, or 6; and 
         z equals 0 if y equals 0 and z equals 1 if y equals 1 to 6; 
         and wherein the method comprises contacting the composition with a modifying resin which is with ether functionalities comprising at least one unit of formula (II):
   —[CH(R 5 )—(CH(R 6 ))q-O]r-  (II)
 
 
       
       wherein q is 0 or an integer of from 1 to 4,
 r is an integer of from 2 to 20, and 
 R 5  and R 6  are each independently hydrogen or C 1-4  alkyl and is capable of changing a position of a selective reflection band exhibited by the chiral liquid crystal precursor composition that is cured. 
 
     
     
       16. The method of  claim 15 , wherein a position of the selective reflection band is increased by the modifying resin by at least 5 nm. 
     
     
       17. The method of  claim 15 , wherein the chiral liquid crystal precursor composition that is cured is adapted to form part of a marking on a substrate.